G10 is heavier then Carbon of the same thickness
G10 Isnt as stiff as Carbon of the same thickness
G10 Is Cheaper
G10 will flex more before it breaks
G10 doesnt conduct electricty (something to consider also)

The usual thing though, atleast for helicopters, is that carbon is superior to G10 for frames. I wouldnt go back to G10 frames in a million years. If you crash your quad, both are going to break anyhow.

I need to get Carbon Fiber Square tubing, is it better to have a round hole or a square hole in the center? Or does it not really matter. (the square hole would have 1.5mm walls and the circle has 1.5mm diameter) ...square hole is cheaper.